金属离子在酿酒酵母钾离子激活型醛脱氢酶作用机制中的作用。
The role of the metal ion in the mechanism of the K+-activated aldehyde dehydrogenase of Saccharomyces cerevisiae.
作者信息
Dickinson F M, Haywood G W
机构信息
Department of Biochemistry, University of Hull, U.K.
出版信息
Biochem J. 1987 Oct 15;247(2):377-84. doi: 10.1042/bj2470377.
The effect of K+ on assays of the enzyme was studied and it appears that the activation occurs slowly by a two-step process. Kinetic measurements suggest that the enzyme-catalysed reaction can proceed slowly (0.4%) in the complete absence of K+. The enzyme exhibits a K+-activated esterase activity, which is further activated by NAD+ or NADH. Stopped-flow studies indicated that the principal effect of K+ on the dehydrogenase reaction is to accelerate a step (possibly acyl-enzyme hydrolysis) associated with a fluorescence and small absorbance transient that occurs after hydride transfer and before NADH dissociation from the terminal E-NADH complex. The variation of activity of the enzyme with pH was studied. An enzyme group with pKa approx. 7.1 apparently promotes enzyme activity when in its alkaline form.
研究了钾离子对该酶测定的影响，结果表明激活过程是通过两步缓慢发生的。动力学测量表明，在完全没有钾离子的情况下，酶催化反应仍能缓慢进行（0.4%）。该酶具有钾离子激活的酯酶活性，且这种活性会被烟酰胺腺嘌呤二核苷酸（NAD⁺）或烟酰胺腺嘌呤二核苷酸磷酸（NADH）进一步激活。停流研究表明，钾离子对脱氢酶反应的主要作用是加速一个步骤（可能是酰基酶水解），该步骤与氢化物转移后、NADH从末端E-NADH复合物解离前出现的荧光和小吸光度瞬变有关。研究了该酶活性随pH值的变化。一个pKa约为7.1的酶基团在其碱性形式时显然能促进酶活性。
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